The invention relates to an apparatus and method for stepwise automatic loading and unloading of a coating apparatus with disk-shaped substrates, especially for data storage technology. This apparatus consists essentially of a magazine with a first turntable on which a plurality of posts are disposed for receiving the substrates.
The substrates to be coated are admitted through an airlock individually into a vacuum chamber by means of a transfer system, and after coating they are again deposited onto a holding post by the transfer system.
The operation of such an apparatus can be considered to be quasi-continuous on account of the stop that occurs between the individual stages for the entry and exit actions, and due to the stationary coating procedure.
U.S. Pat. No. 4,886,592 describes an apparatus based on the carousel principle for the coating of substrates. In this case a rotatable substrate holder is disposed in a vacuum chamber, and on it a plurality of substrate holding posts are provided. A corresponding number of substrates can be transported stepwise on a circular path from one airlock station successively through at least one coating station to the other airlock station by means of a drive. The stepping width of the drive on the one hand, and on the other hand the angular attitude of each coating station to the airlock station associated with it with respect to the axis of rotation of the substrate holder, are selected such that one and the same coating station is associated by the stepping movement with a specific substrate post and the same airlock station.
In the operation of such apparatus, the so-called loading stations by which an automatic loading and unloading of such apparatus is possible are important. Such loading stations in connection with the corresponding magazines are comparatively expensive and complicated, and their cycling frequency is of great economical importance to the economical operation of the coating apparatus, for example for the production of Compact Disks, referred to hereinafter as CD's.
In the state of the art, therefore, loading and unloading apparatus are known which provide the substrate magazine with two turntables, and which therefore occupy a large amount of space.
On the other hand there is a problem in the fact that the transfer arms of the transfer system pick up a substrate from a magazine and transfer it to the coating apparatus, and simultaneously a second transfer arm returns a substrate from the coating apparatus to another magazine. Thus each of these two transfer arms can serve only two stations, namely a magazine loading station and a magazine unloading station. As soon as all the substrates have been taken from the post that is situated at the loading station, the turntable is usually rotated to another station, so that the unloaded post is then removed by hand and placed upon the unloading station of the other turntable. Then this post is again loaded with substrates which return from the coating apparatus.
Since not only CD's but also the titles identifying them are processed on one and the same coating apparatus, the machine is idle when changing from one title A to a title B; as soon as the last CD with title A has been removed from the turntable of the magazine, usually the coating apparatus is at first "run empty." Otherwise the CD's of different titles A and B returning from the coating apparatus to the magazine would be deposited on one and the same post.